The present invention relates to a crystallized, molded product of a polyarylene thioether (hereinafter referred to as PATE) resin.
More in detail, the present invention relates to a highly crystallized, molded product of PATE resin, which is obtained by the process comprising the steps of (1) stretching a melt-molded product of PATE, (2) preliminarily crystallizing the stretched product by treating with an organic solvent and (3) highly crystallizing the treated product by thermal treatment.
Further, the present invention relates to a highly crystallized and tough molded product of PATE resin, which is small in dimensional deformation and wavy wrinkles on the surface, and is high in heat-resistance, bending-resistance and transparency.
As PATE resin, such as polyparaphenylene thioether resin, etc., is one of the engineering resins excellent in heat resistance, moisture resistance, chemical resistance, flame retardance and mechanical properties and these properties can be given to the resin only when it is crystallized sufficiently, it is extremely important to increase the crystallization degree of molded products of PATE.
However, when an amorphous molded product of PATE resin is thermally treated to crystallize sufficiently without applying a large stress (tension, compression, etc.), coarse spherulites usually develope in the molded product and it becomes brittle or opaque and at the same time, uneven relaxation and contraction occur on the product, thereby causing a dimensional deformation and wavy wrinkles. Accordingly, there has been a severe problem that the original shape of the molded product cannot be maintained through the thermal treatment.
Consequently, it was extremely difficult to treat a melt-molded product thermally, with no stress applied, without causing embrittlement, dimensional deformation and wavy wrinkles and maintaining the original shape and transparency. For extrusion molded products such as sheets, plates, pipes, profiles and blow bottles, for which it is difficult to apply stress, it was especially difficult to treat the product thermally.
Thereupon, the present inventors once developed a method of treating the molded product of PATE with an organic solvent, which has an affinity to PATE, to crystallize it highly with no applied stress, without having wavy wrinkles (Japanese Patent Application No. 61-12,889 (1986)). However, there was a problem in achieving the high crystallization by this method since the treatment takes a relatively long time.
Then, the present inventors developed a method of obtaining a highly crystallized, molded product within a short time having substantially no dimensional deformation nor wavy wrinkles by combining the already described method (Japanese Patent Application No. 61-12,889 (1986)) with a thermal treatment. Namely, the molded product is preliminarily crystallized by a solvent and then the preliminarily crystallized product is treated thermally (Japanese Patent Application No. 61-296,454 (1986)). However, it has been recognized that the method sometimes makes the product brittle and opaque.
The present inventors have further extensively studied methods to highly crystallize a melt-molded product by thermal treatment with no or substantially no stress without making the product brittle or opaque and without any accompanying dimensional deformation and wavy wrinkles, and finally, they have found the following unexpected results.
When a method which comprises steps of preliminarily crystallizing a melt-molded product at a low temperature with an organic solvent having a sufficient affinity to PATE resin and of thermally treating the crystallized product (already described in Japanese Patent Application No. 61-296,454 (1986)), is combined with a stretching step, namely, when a melt-molded product is stretched at least in one direction, preliminarily crystallized by an organic solvent, and then highly crystallized by thermal treatment, a highly crystallized molded product can be obtained in a short cycle without becoming brittle or opaque and without accompanying dimensional deformation and wavy wrinkles, therefore maintaining original shape and transparency. Furthermore, since the elongation of the highly crystallized molded product at high temperature is large, another effect has also been found, i.e., that the molded product can be easily remolded by compression molding or stretching at high temperature.
The present invention has been attained based on these findings.